We have developed an organ culture system for human epididymis where the tissue can be kept for up to 8 days and in which addition of physiological concentrations of androgens elicits a response in terms of increased net protein synthesis and cell size. Preliminary results suggest the synthesis of 5 proteins which are secreted to the lumen of the organ where at least 2 of these bind to spermatozoa. Other evidence suggest a sequence in the utilization of androgen by the tissue involving transformation of testosterone to 5Alpha DHT, binding to a cytoplasmic receptor and transference of the complex to the nucleus with prolongued retention therein. We propose the further characterization of the system by comparison with known responses of experimental animal epididymides to androgen stimulation. The specific aims are: 1) to characterize the kinetics of andregoe-receptor interaction and their movement within intercellular compartments and study their control by androgens; 2) The metabolism of androgens in the cultured tissue and the regulation of enzymatic activities by androgens; 3) To study the synthesis of bulk protein, RNA and DNA and the influence of hormones, mainly androgen produced by the tissue in response to androgens and which interact with spermatozoa. For specific aims 1 and 2 we will study, in the absence and at timed intervals after addition of androgen, the distribution of receptor, the metabolization of the substrate and accumulation of metabolites in subcellular fractions. The exchange technique for determination of receptor sites has already been adapted to this tissue. We will also examine changes in the number of binding sites and 5Alpha reductase and 3 hydroxysteroid dehydeogenase activities in cultures with and without androgens for up to 8 days. For 3) we will study the incorporation of labelled precursors of protein, RNA and DNA in cultures additioned with different androgen at various concentration and the possible effect of prolagen-dependent and that interact with spermatozoa, which are likely to be involved in sperm maturation. It is hoped that this research will help characterize a system which can be useful for the study of epididymal physiology.